How do I stop avast home edition from doing a complete check of my computer whenever I do a restart
Welcome to the forum! 
Do you mean the boot scan?
It is just one time (after you have installed the software), not everytime you start the computer.
If you want to schedule a boot scan…see this link:
avast doesn’t do a complete scan of your system on boot unless you schedule it to do so or after avast is first installed to give you a clean start state.
As Bluesman said it is a one shot deal, no more after first installation and reboot unless you schedule it and then it is still a one shot deal.
How to disable scan at boot?
Could you please start regedit, go to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager, select the value BootExecute and export it to a file? If you could post the file as an attachment here, I would like to check what could be wrong there.
In XP, if you press F8 when starting Windows and select ‘Last known good configuration’ from the boot menu, the boot scan should not be started.